This blog follows and explains the processes behind interesting geological events. The emphasis is on those events that are energetic, explosive, and have led to, or have the potential to lead to, disasters.

Welcome!

This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Wednesday, August 13, 2014

Weather extremes, atmospheric rivers and Japanese fire bombs

A shot-down Japanese fire balloon
reinflated by the US
File uploaded by Bkwillwm to
Wikipedia, public domain

In my book, "The Dynamics of Disaster" (Norton Press, 2013), I discuss the big "rivers in the sky"--our jet streams. These atmospheric rivers were discovered in the 1920s by Wasaburo Ooishi, a Japanese meteorologist studying the dynamics of the atmosphere near Mount Fuji. To quote my book: The Japanese "were able to turn their knowledge of the jet streams to their advantage during the war by launching balloon attacks on the US, sending 9,000 "fire balloons" aloft to travel thousands of miles east. Some 300 made it to US soil, and six people died when a family approached one and it exploded. (These were the only known deaths by enemy action on continental US soil during World War II.)"
In a new study by Dim Coumou and a team from Potsdam Institute for Climate Impact Research published August 11 in the Proceedings of the U.S. National Academy of Sciences (ref. below), Coumou points out that the large number of very high-impact extreme weather events over the past decades has seemed out of proportion to the rate of warming of the atmosphere caused by increased CO2. The authors rely on, and quote, an earlier paper in PNAS by Petoukhov, et al. (of the same institute) reporting the same thing: the frequency of these extreme events over the past decade is such that it is unlikely to be just a "stochastic mechanism of extremes."
And, here's where the Japanese discovery of the jet stream becomes relevant, because it's in the jet stream that the changing flow patterns are driving the weather extremes.

Again, quoting from my book: "Flowing at the top of the troposphere, the jets have variable elevations between 12,000 and 80,000 feet...[They] can be several hundred miles wide and 1-2 miles deep, and they can flow at speeds of up to 400 mph. Jet stream winds generally flow from west to east, but they have a loopy structure and flow in various directions, even "backward," from east to west, in some segments. The looniness, known as a Rossby wave, has a wavelength of about 1,800-2,400 miles and arises primarily because the Coriolis effect has different strengths at different latitudes. The jets can split apart, re-join, reverse, or simply stop.When the Rossby waves move to the north, they suck warm air northward, e.g., from the tropics into Europe, Russia, or the US. They do the reverse when they move south, transporting cold air from the Arctic to the south. " I then go on to explain how the position of the jet stream and the Rossby waves influenced the position of Hurricane Sandy in October 2012.
Now back to the research of Coumou and his team: According to the theory advanced in the article (based on analysis of meteorological conditions from 1979 to 2012), there are resonances in the atmosphere that trap the Rossby waves into certain configurations for long periods of time. Thus, a heat wave that would not be dangerous if it were a few days long, becomes extreme when its duration increases. (The paper is limited to analysis of the Northern Hemisphere.)
The speed at which a wave travels along the jet stream (the "phase speed") is, in one approximation, directly proportional to the mean zonal wind speed. To first order, synoptic waves with a wave number (k) equal to 6-8 travel at this speed. The zonal mean wind speed changes with season, being less in the summer. Because the zonal mean wind speed is lower in the summertime, the phase speed is also lower because of this direct proportionality. In fact, in the "boreal summer"--July, August--the phase speed can be close to zero (the waves are quasi-stationary, especially for wave number 6) or even negative (that is, the waves would travel to the west instead of the east). This weakening of the zonal wind speed and, hence, the wave speed is one mechanism explored. Free-traveling waves are simply slowed down or stopped. If the waves are stationary, then the troughs and ridges of the Rossby waves are stationary, setting in the northerly or southerly flow of air for long periods.
The second mechanism is the amplification of quasi-stationary waves by resonance between free and forced waves in the midlatitudes. Looking at the Petoukhov et al paper, the quasi resonance hypothesis is as follows. (1) Generally, the large-scale atmospheric circulation at mid latitudes is characterized by traveling Rossby waves with zonal wave numbers (k) equal to or greater than 6 propagating in the longitudinal direction at a phase speed of c~6-12 m/s as discussed in the paragraph above. (2) The circulation is also characterized by quasi stationary planetary-scale Rossby waves with c~0, frequency w~0, and various zonal wave numbers m that develop in response to orographic obstacles or weather sources and sinks, that is, to "conditions in the atmosphere that differ from place to place on the earth. Their hypothesis is that during the extreme summer events, persistent wave structures with high amplitudes evolved and made an unusually large contributions that the usually weak midlatitude response to the thermal and orographic sinks was strongly magnified at wave numbers 6,7 and 8.
They assert that the apparent cluster of resonance events observed in their data set (see their figure reproduced above) is due to an increased wave 7 and 8 resonances, and that furthermore, these resonances high in the atmosphere are coupled to persistent weather patterns at the surface, and thus the extreme weather events. The changes observed are statistically significant at the 95% confidence level.
The theory and data (from 1979-2012) suggest that because of warming in the Arctic, temperature differences between the Arctic and tropics are decreasing. Temperature differences drive the atmospheric circulation patterns, and changes in these differences (the temperature "gradients") are causing the atmospheric circulation patterns to change. Although much more detailed work and analyses needs to be done, their tentative projection (Figure 7) of conditions a century away shows t"similarities with the recently observed anomalies). According to RCP8.5 climate model (one in which we don't curb our CI2 emissions very much), the July-August thermal gradients will increase northward of 50N and decrease southward of 50N, leading to strengthening of the sub polar jet and weakening of the subtropical jet.

**I have used the report in ScienceDaily.com for parts of this post: http://www.sciencedaily.com/releases/2014/08/140811170106.htm

The abstract for the Coumou PNAS article is here and the full text is here.

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==>My book:The Dynamics of Disaster <==

Published by W.W. Norton--Click on image to go to Amazon.com

Synopsis of Book and Reviews

If you want to learn a bit of the science behind earthquakes, landslides, volcanic eruptions, tsunamis, rogue waves, cyclones and hurricanes, and tornadoes, this is an introduction that weaves together stories of various disasters--some barely known to much of the world--their causes and dynamics, and some suggested actions we can take to protect ourselves. The book is available both in paper and as an audio CD.

"This is a fantastic book. I've recommended to colleagues at FEMA and am using it as a text for my disaster classes. It really demonstrates how knowledge of the environment should inform policy. It was a page turner for me!"--Dr. Trish on Customer Reviews at Amazon.com

''Geologist Kieffer argues that we don't understand disasters as well as we should. She contrasts 'stealth disasters' caused by long-term human impact, including climate change and soil erosion, with natural disasters or 'acts of God,' which are also increasingly affected by human actions . . . [A] highly accessible look at disasters.'' --Booklist

"Kieffer's brisk and lucid presentation has some of the relish with which surgeons reputedly regale each other with tales from the operating theatre. Laid out before the reader are the suppurating wounds, scalds, tremors, and scars acquired by the Earth over millennia, centuries, decades, or minutes."--Claudio Vita-Finzi in The Times of London

"If you are an amateur weather geek, disaster wonk or budding student of the earth sciences, you will want to read this book. (If you're squeamish, skip the chapter titled "A Plague of Snakes.")--Seattle Times by Mary Ann Gwinn

"[T]he clarity of Kieffer’s writing, coupled with her careful choice of supporting graphics, makes the content engaging and accessible to a wide readership." Alison Stokes in TheTimesHigherEducation

“In The Dynamics of Disaster, famed geoscientist Susan Kieffer merges stories and science in a fascinating introduction to the dangerous side of the Earth, with key insights for citizens and enough excitement to captivate the full range of students.”—Richard B. Alley, author of Earth: The Operator’s Manual

"Both general readers and working scientists will enjoy this well-written book--and learn some things they did not know...Summing up: Highly recommended. Lower-division undergraduates through professionals; general audiences."--by Seth Stein in Choice Reviews Online (of the American Library Association), April 2014

"This [impressive] book ought to be placed in the hands of politicians, engineers, insurance assessors and, frankly, anyone who sees sense in understanding the processes and systems that guide our planet." --Geographical, December 2013, by Jonathan Wright

This book is part of a recent trend--one that is just beginning, but is likely to grow--in which scientists, especially young ones, seek to move beyond the "disasters are bad" view presented in beginner classes to a more sophisticated and nuanced view…Seth Stein in Physics World (U.K.)

"It is like a "Magic School Bus" outing for adults, with Kieffer acting as Ms. Frizzle, guiding the reader around the world to disaster hotspots, where she analyzes and breaks down the physical characteristics that contribute to events in those areas."--Summit Daily, December 20, 2013

#1 in list of Best Sellers: Geology, from May 2013 to March 2014. LibraryJournal.com

Victoria Raschke's Reviews (Jan. 09, 2019) Kieffer's explanations of the how natural disasters occur is perfectly suited to the interested layperson. The section on rogue waves was worth the price of admission in that it explains something that always seemed kind of supernatural. If you have any interest at all in understanding our living planet and why it sometimes feels like it would be happy to be rid of us, this is the book for you.